A piece of wood was rubbed against silk. What charges (according to the sign) appeared on a piece of wood and what on silk?

Charges with a “+” sign appeared on the tree, and on silk – with a “-” sign.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.